Swirling water vessel for forming sulfur pellets

ABSTRACT

Molten sulfur streams are caused to contact water in a columnar vessel which includes an impeller disc creating a swirling motion of the water sufficient to cause the sulfur droplets to follow a path which is more or less spiral as they drop through the vessel.

United States Patent [1 1 Elliott Sept. 23, 1975 SWIRLING WATER VESSEL FOR FORMING SULFUR PELLETS [76] Inventor: Herbert James Elliott, The

Bungalow, Bradford-on-Avon, England [22] Filed: Oct. 24, 1972 [21] Appl. No.: 299,863

Related U.S. Application Data [63] Continuation of Ser. No. 820,348, March 17, 1969, abandoned, which is a continuation of Ser. No. 488,039, Sept. 17, 1965, abandoned.

2,278,125 3/1942 Landgraf 259/D1G. 25 3,272,893 9/1966 Mogensen 264/14 X 3,339,897 9/1967 Davis 259/8 X 3,345,235 10/1967 Miller 264/14 X FOREIGN PATENTS OR APPLICATIONS 625,941 7/1949 United Kingdom 425/6 Primary Examiner-Robert D. Baldwin [5 7] ABSTRACT Molten sulfur streams are caused to contact water in a columnar vessel which includes an impeller disc creating a swirling motion of the water sufficient to cause the sulfur droplets to follow a path which is more or less spiral as they drop through the vessel.

8 Claims, 2 Drawing Figures SUL PHUP OUT 49 w m p Invenlor y W a: 9

Attorne$ This invention relates to the treatment of sulphur and like normally solid materials that melt at fairly low temperatures. More particularly, it is concerned with the production of sulphur pellets that can be'handled much more readily and conveniently than molten or block sulphur.

A primary object of the invention is to provide a process for pelletising sulphur that is simple and cheap and which gives externally hard pellets suitable for transportation by, for example, pneumatic handling equipment.

According to the present invention, sulphur or like material is pelletised by being delivered, in the molten condition, into a body of water at substantially atmospheric pressure, and means are provided to keep the resulting globules or droplets of sulphur moving in the water and to prevent them massing or piling up together until in the course of solidifying they have reached a condition, at least externally, in which they do not adhere to one another.

Previous proposals have been made for pelletising sulphur an essential feature of which has been the treatment of the sulphur in hot water under pressure. Since the boiling point of water at atmospheric pressure is below the melting point of sulphur, a pressure above atmospheric has been thought necessary to enable the melting point of sulphur to be reached. By contrast, the technique of this invention affords a process for pelletizing sulphur that is simpler and cheaper than the processes previously proposed, especially in that is does not require operation under pressure.

Another feature of some previous proposals has been the provision of a tall tower, say 40 feet high, through which the droplets of molten feed material could fall while solidifying into pellets. Such a tall tower is a costly piece of equipment to install and maintain. According to a preferred feature of the present invention, a vortex or swirl is created in the body of water in which the pelletisation takes place. This, together with the fact that colder water can be used, enables pellets to be obtained without the need for a tall tower or active agents are added to the water. In the preferred method the added agents are silicones. An important result of using such agents is that the solidifying globules can be allowed to come together at a considerably higher temperature without risk of the pellets adhering to one another. As a consequence there is a saving in equipment, in particular plant for drying the product.

The invention also includes apparatus for carrying out the above'method and the product so obtained.

Methods of carrying the invention into practice will now be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic elevation of a sulphur pea letising plant, and

FIG. 2 illustrates a possible modification of that plant.

Referring to FIG. 1 of the drawings, a molten sulphur becomes quite free flowing, is delivered to a molten sulphur reservoir 11 at the top of a pelletising vessel 12 of short columnar form. The floor of the reservoir 11 is formed by a plate 13 in which are fitted a large number of nozzles 14, say 1 /2 to 2 mms. in diameter, which deliver the molten sulphur downwardly beneath the plate 13 in separate streams. Some distance beneath the nozzle plate 13 but still fairly near the top of the vessel 12 is an impeller disc 15 which is rotated by a vertical shaft '16. The vessel 12 is filled with water to a level well above the disc 15 but a few inches, say 2 inches to 4 inches, below the nozzle plate 13, and the disc 15 creates a vortex or swirl in the body of water.

The molten sulphur streams from the nozzles 14 break up into globules or droplets upon entering the water and are caught up in the swirl or vortex created by the rotation of the impeller disc 15 and caused to follow a path which is more or less spiral as they drop through the vessel. At its lower end the vessel 12, which may be, say, about 3 feet high, has a coned bottom 18 in which the sulphur bodies, now solidifed into pellets, collect and from where they are withdrawn through a trap 17. A screen 19 dewaters the pellets and delivers them in a substantially dry condition, while the extracted water is returned to the vessel 12 via a line 20.

The vessel 12 is operated at atmospheric pressure. The water will, of course, heat up due to the molten sulphur entering it and therefore circulation is maintained to remove the hotter water at the top and replenish lower down with cold. Some of the entering water can be introduced by way of tangential entries 21 at various places in the side wall of the vessel 12 so as to further promote the swirling in the vessel. A heater may be provided around the upper portion of the vessel for controlling the water temperature in this region.

The speed of rotation of the impeller disc should be high enough to prevent any deposit of sulphur on the impeller. The strong vortex water wall directly over the impeller disc and the radial discharge at the periphery of the disc has the effect of breaking up the sulphur droplets to a smaller size whereas droplets falling outside the main vortex near the vessel wall will not be subjected to such a strong action and therefore remain larger. It is, in general, desirable to obtain a product in which the pellets vary in size, as close packing then oc curs to give a high bulk density. It is, however, undesirable that sulphur droplets should be permitted to fall into the comparatively calm centre or eye of the vortex.

To prevent the funnel of air in the vortex from interfering with the satisfactory production of pellets, a barrier element can be mounted above the impeller to check the downward extent of this funnel. The barrier element may be mounted on the impeller shaft to rotate therewith, as at 22, or it may be a fixed element carried, for example, from the wall of the vessel. The interior of the pellets produced appears to be rhombic crystal sulphur while the crust is amorphous. The amorphous crust is hard, smooth and rounded and makes the pellets particularly suitable for handlilng by, for example, pneumatic means.

The impeller disc can be dished or flat. And various configurations'of the blades may be employed thereon. The exact design of the impeller, and its speed, depth of immersion and clearance from the vessel side wall are chosen to suit the circumstances of each particular a yone-7,1;

plant and thenature of the product desiredBy raising andlowering the impelleiit ispos'siblet 'vai'y the sizel of the. pellets produced. Especially good coritrolofpellet size canbeachieved'by the use of a 'skirt 23 (FIG; 2)- 3.-X 'Q Ul'ld the impeller 'which; hasfourinternal deflector humps 24 of smooth arcuate form disposed-equidis. tantly around its periphery To form these humps the skirt223 has four part-cylindrical concavities 25 at 90 intervals.

The skirt 23 v v tend from abovethe water level in the vessel to so me distance below. the level atwhichthe impeller normally operates. 'It is convenient to .use. the, four passages formed between the humps 24 and the. waliof the vessel 1-2 as off-takes for waterflowing upwardly in ';the vessel and there may, ifdesired, be mesh or gauze material, e. g .50 mesh gauze, across the bottom endsof these. passages to prevent carrying' ofsulphur pellets into the overflow, At their upper ends the four passages m ay communicate with an, annular overflow channel,

; If-the impeller is progressively lowered from within thecslrirtto alevel belowitthepel let size will increase, and thereforewe have a simple and inexpensive way of making a p elletising vessel that can berapidly adjusted without dismantling orthe additionor removal or parts, to produce pellets of varying sizes according to the purposefor which they are required. 1 1

. ,Since the pellets constituting the product are. reqniredfor usein adry state, it is advantageous if they leave the vessel.,l2 at a reasonably elevated temperatt re tdassist naturaldrying. We have, discovered that certain .ad'dit'westo the water in the vessel, are especially valuable in this connection. In particulafnsilicone vo ym smay b s to ad ge Thereareniany silicone additives that give beneficial results, but in generaLthose-of higherviscosity are. preferred, suchas Elli/50,000 of, Imperial Chemical Indnstries Limited with .a visco.sity of 30,( )0Q'centistoi es' at: 251C, if riperationat the, more elevatedtemperatures is required The lower viscosity silicones tend t lose their efficacy withrise .in temperature, and a v'i'scesity range-of 30,0QQ-te 100,000 centistokes is preferred. Many silicones require dilution in ,a solvent, forexampletben zene, toluenetor; xylene, before they .-will, disperse in the waterrbody to the best extent. H I

,lt will be, pndersto od that liquidsiliconeswith' sufficientchain length and heat stability are employed, such asidimethyisilieones nd phenyl, substituted p olysiloxanes, ,It is necessary to choose a silicone fluid which does not react chemically with the material being pelletised.

v As to the amount to, be'ad ded this can readily be de ,terminedvfor eachsilicone'by' simple experiment; too

little does notgive therequired resultand too mucheither shows no significant improvement over the correct 1 amount ;-or in some casesresults in the sulphur joining upinto thread of string-like'formations. A few drops per gallon of wateris ordinarily all that is required.

walls or bottom ofnthe vessel Before the globules have tra velied down any substant-ialdistance through the waterit is possible'to collect them while theyare still fairly soft and they will notstick together or to the walls of the collector. They can,

withits concavities preferably eitin apprepg iate-ca'ses, be collected while still at a temperature as high es5,6f C This means that the tempera- O f course, it not necessary to remove the pellets at elevated temperature, If the .pelletising I plant is arranged to cool down thefpe llets to near ambient temperature they will be quite hard and resilient when collectedand ready almost imrnediatelyfor, mechanical handling; they willhardenstili furtherlandlose their resilience,onstOring...Furthermore, the swirling action still has .the substantial advantage of producing .pellets without significant perforations, by creating a kneading or rolling action on the pellets evenif reason of the additive it is, notinecessary fer the purpose ofpreventing the solidifying pellets from stickingtogether or to the vessel, d V I v T-Certain previous proposals for thepe lleti sing of sulphur havezresulted in the ferrnation ofpellets with hollow centres or a weakening tunneli hole thererindue to free verticalfall of the droplets in water. Thepresent technique helps to reducethe size of ,thishole; in particular, the rnotion of the vortex has .this d esirable-effeet, Under favourable circumstances the holecan be reducedto a-meredent. M; t

Qther specific ,silicones thathave been found effective, especially at the lower temperatures, are S ilcolapse437 (diluted to .l 0 before use), others in; the

F1 11 ,series (Imperial Chemieal IndustriesLimited), MS. 510, M8550 and. MS .Antifoam emulsions RD and FG (diluted to .l 0%);Midiand .Silicones Limited). Some require to be used at rather higher. concentration (say 12 drops per gallon ot more).

' While silicones are.the preferred.additives,certain ,other polymeric materials have ;been found effective, particularlywater soluble compounds. Thus polyethylene and polypropylene oxide compounds, apolyacrylamides and.- polysulphites are effective to, varyingdegrees; TheseJnater-ials have alimited temperature in conjunction with sili cones v With regard to the plant, it is' beneficialin certain cases to slant the sulphur injection nozzlesbut the amount and whether it is wi-thor against the flow depends on the particular additive used, Consequently, it

- "may beadvantageous to fit swivel nozzles to allow for use of different additives,

nozzles.

Many modificationsare possible without-departing from the scope of the invention. Other forms of stirrer are possible, and mechanical stirring can be'dispensed with if the vortex or swirl isrproduced entirely by'means 'of tangential water. jetsdisposed at intervals around, and up; the height of,.the vessel i i Y The method and apparatus described enablessulphur pellets-to be produced, withamoisture. content of less th'an l%=b y weight, which we believe has not been possible previously'because of moisture locked inside the pellets. Test results on samples of product obtained gave moisture contents, after drying, of the order of 0.02% by weight. Also the pellets are hard and tough and well suited to pneumatic handling techniques.

I claim:

1. An apparatus for continuously forming discrete sulphur pellets comprising, in combination:

a columnar vessel with a coned bottom portion adapted to operate at atmospheric pressure and filled to a predetermined level with water;

a static reservoir for molten sulphur at the head of said vessel and spaced a short distance above said water level;

a plurality of apertures disposed in the floor of the reservoir, said apertures being adapted to deliver molten sulphur from the reservoir in separate downward streams that fall substantially vertically into the water in said vessel;

means providedin association with said vessel to create a continuous swirlihgmotion of said water sufficient to cause sulphur droplets to follow a more or less spiral path through said vessel; and

a trap valve for removal of pellets collected in said coned bottom portion.

2. An apparatus according to claim 1 wherein the means for creating the swirling motion comprises a rotary impeller within said vessel.

3. An apparatus according to claim 2 wherein the impeller is vertically adjustable.

,4. An apparatus according to claim 2, including a water inlet at the bottom of said vessel and a water outlet near the top thereof.

5. An apparatus according to claim I wherein the means for creating the swirling motion comprises tangential water ehtry jets disposed at the sides of the vessel.

6. An apparatus according to claim 2, wherein a barrier plate is mounted in the column near the top thereof above the impeller to check the downward development in the water of any vortex cavity created by the swirling motion.

7. An apparatus according to claim 2 wherein means is providedin the column around the region containing the impeller to deflect back inwardly toward the impelleimaterial impelled outwardly thereby.

8. An apparatus according to claim 7 wherein the deflector means comprises a sleeve disposed coaxially within the column and having at its periphery at least one inwardly-projecting hump. 

1. AN APPARATUS FOR CONTINOUSLY FORMING DISCRETE SULPHUR PELLETS COMORISING, IN COMBINATION: A COLUMAR VESSEL WITH A CONED BOTTOM PORTION ADAPTED TO OPERATE AT ATMOSPHERIC PRESSURE AND FILLED TO A PREDETERMINED LEVEL WITH WATER: A STATIC RESERVOIR FOR MOLTEN SULPHUR AT THE HEAD OF SAID VESSEL AND SPACED A SHORT DISTANCE ABOVE SAID WATER LEVEL: A PLURALITY OF APERTURES DISPOSED IN THE FLOOR OF THE RESERVOIR, SAID APERTURES BEING ADAPTED TO DELIVER MOLTEN SULPHUR FROM THE RESERVOIR IN SEPARATE DOWNWARD STREAMS THAT FALL SUBSTANTIALLY VERTICALLY INTO THE WATER IN SAID VESSEL: MEANS PROVIDED IN ASSOCIATION WITH SAID VESSEL TO CREATE A CONTINUOUS SWIRLING MOTION OF SAID WATER SUFFICIENT TO CAUSE SULPHUR DROPLETS TO FOLLOW A MORE OR LESS SPIRAL PATH THROUGH SAID VESSEL: AND A TRAP VALVE FOR REMOVAL OF PELLETS COLLECTED IN SAID CONED BOTTOM PORTION.
 2. An apparatus according to claim 1 wherein the means for creating the swirling motion comprises a rotary impeller within said vessel.
 3. An apparatus according to claim 2 wherein the impelLer is vertically adjustable.
 4. An apparatus according to claim 2, including a water inlet at the bottom of said vessel and a water outlet near the top thereof.
 5. An apparatus according to claim 1 wherein the means for creating the swirling motion comprises tangential water entry jets disposed at the sides of the vessel.
 6. An apparatus according to claim 2, wherein a barrier plate is mounted in the column near the top thereof above the impeller to check the downward development in the water of any vortex cavity created by the swirling motion.
 7. An apparatus according to claim 2 wherein means is provided in the column around the region containing the impeller to deflect back inwardly toward the impeller material impelled outwardly thereby.
 8. An apparatus according to claim 7 wherein the deflector means comprises a sleeve disposed coaxially within the column and having at its periphery at least one inwardly-projecting hump. 